Rage128 compatibility via Radeon drivers isn't very likely. When introduced the Radeons were significantly different then the Rage128. As I had one of the few fairly high clocked Rage128 cards (with an ATI Theater chip on it), I was always fond of that series (nice video quality).
I've never gotten confirmation, but I've always suspected that the Radeon's design was influenced by the people and technology that was brought into ATI by the buy out of ArtX.